1. Field Of The Invention
This invention relates to a structure for a wiper arm used for an electric windshield wiper to wipe a windshield of an automobile or the like with a wiper blade.
2. Description Of The Prior Art
The prior art wiper arm 100 shown in FIGS. 9-11 includes a connecting portion comprised of retainer 101 made of stainless steel for fixing a wiper blade and an arm head 102 made of ADC material (Aluminum alloy die casting) adapted to be connected with a wiper motor. In the Figures, numeral 103 designates a connecting pin, numeral 104 designates a metallic collar and numeral 105 designates a metallic bushing. As shown in FIG. 11, the cylindrical bushing 105 is fitted into an opening 102a bored in the arm head 102 and the cylindrical collar 104 is inserted into a hollow portion 105a of said bushing 105, the retainer 101 is in contact with right and left ends of said collar 104 as shown in the Figures and the connecting pin 103 extends through the opening 101a bored in the retainer 101 and a hollow portion 104a of the collar 104, and then the retainer 101 is connected movably with the arm head 102 by flattening the protruding portion of the connecting pin 103 out of the retainer 101.
Numeral 106 designates a tension spring, which is hooked in a holder 101b equipped on the retainer 101 at the end of left side thereof in FIG. 9 and hooked on a roller pin 108 attached to the arm head 102 through a hook 107 at the end of the right side thereof which energizes the retainer 101 counterclockwise relative to the arm head 102 in FIG. 9.
However, in the conventional wiper arm 100 as described above, because it has a structure wherein the metallic bushing 105 is fitted into the arm head 102 made of ADC material, and the metallic collar 104 is inserted into the bushing 105 with the retainer made of stainless steel making contact with both ends of said collar 104, an electrochemical cell (a local cell) is formed between arm head 102 and retainer 101 and an electric current flows through the collar 104 and the bushing 105. Consequently, electrochemical corrosion sometimes occurs in the arm head 102 and retainer 101, so that there is a problem that it spoils the beauty of the wiper arm 100.